Some theologians might use the term “open” in the context that it was still debated, but as I said earlier Councils had already laid the foundation for what the Canon was for the Catholic Church. But as I said, the Solemn Definition language was not used at the Council of Florence in 1442 because the level of debate was not the same as what happened in the 16th century.
So my take, the level of Definition directly corresponds to the level of attack or questioning on Doctrinal point.
And lets be honest, many of the original protestants were wanting to throw out some of the 27 NT books as well.
You like to lean on prior councils as the final word on issues.....but to you adhere to everything they advanced?